Medical syringe



July 13, 1948.

5. J. EVERETT MEDICAL SYRINGE Filed Dec. 29, 1944 gwue/wbo'v 5/7/1062. J/i/VE-S EVEKEF;

Patented July 13, 1948 1, mSa'muel J amesEVerett, Thornton Heath', England jnmiueation Diseas 29, 1944, Serial itbgsrasss i ,In Greatfiritain December 1, I943 2Claims. (Cl. 12821) a l -.,..Thi s invention relates to medical syringeslsuch ss hy-poderinic syringes. Hitherto these syringes have beenjof two maintypes. I'nlone the barrel jcomprises a glass cylind losed by a metal member. carrying the nozzle, such ah arrangement the metal'plosure member is formed withan'annular recess considerably largerthan theedge of the cylinder wall and the cylinder is secured to the closure member by applying a low-fusion solder, which melts at about 150 C., in a plastic state to the recess, the end of the barrel then being inserted into the plastic mass which is thereupon allowed to cool to lock the barrel in position. An objection to this type is that the joint will not stand high sterilizing temperatures and another objection is that the medicamentcomes into contact with the metal. Such disadvantages are absent from the other main type in which the front closure member is of glass moulded from the end of the glas cylinder, but such an all-glass barrel has a very friable nozzle and consequently a short life. In the specification of my British Patent No. 557,363 I have described a syringe comprising a glass cylinder having welded thereto a ceramic front closure member with an integral nozzle. This is superior to both the aforesaid main types in that the ceramic is extremely robust, the medicament does not make contact with metal, and the assembly may be constructed so as to withstand substantial temperatures.

The present invention is concerned with further advantageous ways of providing a medical syringe which has these advantages.

According to the present invention, a medical syringe having a glass barrel and a ceramic front closure member is reinforced at its forward end by a metal band which surrounds the lower end of the barrel so as to bind a ceramic front closure member of robust dimensions within the barrel. Glass, according to some authorities, has a tensile strength of between 2,000 and 3,000 pounds per square inch, but is strong in compression, while a technical porcelain, such as that known as steatite, has a tensile strength of about 10,000 pounds per square inch; and, therefore, where a steatite front closure member is employed in this form of the invention, good use is made of the properties of the different materials because the steatite is used for the part that is liable to substantial rough usage while the glass barrel is maintained mainly under compression, being nipped between the closure member and the metal band.

In order that the invention may be clearly understood and readily carried into effect, an exf 'will now be described in "detail'with reference to the accompanying-Figure fwhichi's a -seeeqnars1evatiea, on 'a very greatly enlarged scale; f the forwardendof amedical syringe-* 1 In the jconstruction shown in Figure 13a front closure member 12 is fitted into the end" of a simple glass" barrel l3 and boundin position by a metal band l4 encircling the glass barrel l3. The front closure member is preferably made of a ceramic material. So that substantial stresses are not set up if the syringe is sterilized by subjecting it, for example, to a dry heat of 160 C., it is very important for the coefficient of thermal expansion of the ceramic material to match that of the glass from which the barrel is made. The coeflicient v of thermal expansion of the ceramic material should be the same as, or slightly less than, that of the glass and it should not be greater. In practice it is found that a coefficient of thermal expansion of about 6.0 10 is very suitable for the ceramic material and this is matched to a socalled neutral glass having a coeificient of ther: mal expansion of about 6.5 10- Other combinations of glass and ceramic material may, however, be employed.

. In the manufacture of the example in Figure 1,

a glass syringe barrel I3 is carefully prepared and its bore lapped so as to provide a perfectly smooth surface of the exact dimensions required, The ceramic closure member is moulded from a steatite mixture containing about talc and the usual fluxes, the ingredients being chosen so as to provide the desired coefficient of thermal expansion. The outside diameter of the closure member I2 is lapped so as accurately to fit inside the lower end of the barrel. The metal ring I4, whichmay be between /a inch and inch wide and which has moulded on its inner surface a white metal alloy comprising 97% tin and a. further ingredient to impart stiffness, is applied in a heated condition about the barrel I3 so that, on cooling, the lower end of the latter is compressed between the periphery of the closure member l2 and the encircling metal. In this manner the barrel is clamped to the closure member so as to secure the latter in position. The white metal alloy is chosen so as to withstand high sterilizing temperatures such as the aforesaid C., the mode of construction being such that the metal alloy is used effectively and when the syringe is sterilized, the glass is not fractured and no dangerous strain is set up in the end of the cylinder.

In a modification of the construction of Figure 1 the outside of the cylinder is formed at its lower as said glass barrel, and a metal ring disposed on the barrel and adjacent the front endthereof for clamping said barrel to said front closure member, said metal ring having an internaldiameter less than the normal external diameter of said glass barrel, the front parrot *sai'd barrel being thus compressed by said ring into cl'ain'pin'g engagement with said closure member. 2. A medical syringecomprising a glass barreLa-teohnical porcelain front closurermember having an integral hozzle portion at one end, the other end of said porcelain closure member extending into and in sliding contact: with the front end of said barrel, said front closure member haying-substantially the same coeflicien't oi expansion as said glass barrel, and a. metal ring shrunk on the barrel and adjacent the front end for clamping said barrel to said front closure member, said metal ring having an intemal diameter less than the normal external diameter of said glass barrel, the front part of said barrel being thus compressed by said ring into clamping engagement with said closure member.

SAMUEL JAMES EVERETT.

meanness ones 7' 1 The following references are of record in the die of this patent:

UNITED STATES PATENTS 1% Number Kaine Date 1,31 5,8 Wackenhuth Sept. 9, 1919 ;1 ,3 i8-, 4;1 2 'Har'rih'ran Aug, 3, 1920 1,549,606 Kazmansky Aug. 11, 1925 6 FOREIGN PATENTS Number I Country Date 289,654 may :44 Oct. 23, 1 931 gaiiar-ege Framed Mar. 21:, 191'? 491-3321 Great Eritain 4A Nev. 3,1933

25 I 557,363 Great Britain Nov. '17, I943 

